Economia de nado e tempo limite à velocidade mínima de vo2max: novas descobertas

A economia de nado é uma área de investigação que teve como pioneiros, em Portugal, Vilas- Boas (1993) e Alves (1995). Passada uma década, novos momentos experimentais foram realizados e resultados up to date foram obtidos. As mais recentes metodologias foram empregues e, inclusivamente, uma nova área de treino parece ter emergido - o tempo até à exaustão à intensidade de nado correspondente à Potencia Aeróbia, isto é, ao consumo máximo de oxigénio (VO2max)

Determinant kinantropometric factors in swimming

O objetivo deste trabalho é apresentar uma revisão bibliográfica das principais características cineantropométricas do nadador e a forma como estas influenciam a sua prestação na modalidade. As principais conclusões obtidas foram as seguintes: (i) os nadadores são mais altos e pesados do que a população em geral; (ii) os nadadores apresentam um elevado índice envergadura/altura, explicitando valores elevados do diâmetro biacromial e do comprimento dos MS; (iii) verifica-se uma elevada razão entre os diâmetros biacromial e bicristal, traduzindo um fator decisivo na modalidade: a promoção de um coeficiente de arrasto inferior; (iv) foram observados elevados valores de comprimento e superfície dos membros dos nadadores (afetando positivamente a sua capacidade propulsiva); (v) os nadadores de elite apresentam um somatótipo médio ecto-mesomorfo e as nadadoras são centrais ou mesomorfas equilibradas; (vi) como grupo, os nadadores apresentam um maior percentual de massa gorda do que outros desportistas, fator este que poderá beneficiários relativamente à sua flutuabilidade.The aim of this work is to present a bibliographic review, based on the specialized literature, of the kineantropometric characteristics of swimmers and their importance for swimming performance. The main conclusions were: (i) swimmers are taller and heavier than the general population; (ii) swimmers present an high index of arm span/height (explained by a large biacromial diameter and long the upper arm); (iii) high values for the biacromial/bicristal diameter ratio were found, offering a lower drag coefficient; (iv) high length and surface area arm and leg values were observed (which positively influence their propulsion capacity); (v) elite male swimmers presents a ectomorph-endomorph somatotype and elite female swimmers are central or balanced mesomorphs (vi) swimmers exhibit a higher percentage of body mass than other athletes, which may benefit positively their floatation

Relationships between some well known indicators of aerobic resistance of swimmers

The concept of the anaerobic threshold (AT) at swimming velocity corresponding to 4 mmol.l-1 blood lactate concentrations (v4), introduced by Mader et al. (1976) and further developed by following authors, was used by a large number of scientists and swimming coaches for training and diagnostic purposes. Although it's considered a good indicator of aerobic capacity of swimmers, some authors disagree of that fixed value, arguing that the individual AT varies a lot, namely between 2 and 5 mmol.l-1 (Madsen e Lohberg, 1987). The purpose of this study is to verify the adequacy of the v4 in swimming, comparing it with two other valid indicators of the AT: critical velocity (cv) and the mean velocity of the 30 min test (vT30). Subjects were 30 juvenile swimmers of the Porto regional swimming team (with ages between 12 and 15 years). V4 was determined according to the 2 x 400m protocol, being the first repetition performed at 85% of the personal best and the second one at maximum speed (a rest period higher than 30 min was respected between repetitions). Samples of 25 μl of capillary blood were collected at 3, 5 and 7 min of recovery and analysed for blood lactate concentration with an Accusport analyser (Boheringer Manheim). CV was assessed based in the results of maximal tests of 100 e 400m and was considered as the slope of the regression line calculated between the test distances and the respective times. The ratio between the distance achieved and the duration of the test, i.e., 30 min of continuous swimming assessed the vT30. The mean values of the different variables are presented in Table 1. These results showed that the mean values of v3, v4 and v5, cv and vT30 are very similar; only v8 is statistically different of some other parameters (v3, v4, cv and vT30). We can also see strong positive correlation (r³0.91) between all the parameters (with exception of v8) regardless the stronger values between V5 and the other two tests.info:eu-repo/semantics/publishedVersio

Predicting the intra-cyclic variation of the velocity of the centre of mass from segmental velocities in butterfly stroke: a pilot study

The purpose of this study was to analyze the relationship between the intra-cycle variation of the horizontal velocity of displacement of the center of mass (dV), the hand’s and feet’s velocity, as well as, to identify the variables that most predict the dV’s, in butterfly stroke. The study was divided in two parts. The aim of Part I was to investigate the behavior of variables in study at slow swimming velocities and the purpose of Part II was the same but at high swimming velocities. 3 male Portuguese swimmers and 1 female swimmer, of international level were studied in Part I. The swimmers were submitted to an incremental set of 200 m butterfly swims. In the Part II, 7 Portuguese male swimmers of national and international level were studied. Each swimmer performed two maximal 25 m butterfly swims. Both protocols were recorded from four different plans, allowing a 3D analysis. It was calculated the dV, the 3D components (Vx, Vy, Vz) of the hand’s velocity and the 2D components (Vx, Vy) of the feet’s velocity. Several variables presented significant correlation coefficients with dV at all selected velocities (high velocity ranged from r = 0.58 for Vx-out to r = 0.82 for Vy-1dwn; slow velocity ranged from r = -0.45 for Vx-1dwn to r=0.73 for Vx-ups; overall velocity ranged from r= 0.34 for Vz-ent to r = 0.82 for Vx-ins). It was also computed a regression model to predict dV. For high velocity (up to 1.75 ± 0.09 m.s-1), the variables that best predict dV were Vy during the first downbeat, Vx and Vy during the arm’s insweep (r2 = 0.93). At slow velocity (up to 1.48 m.s-1), the variables included in the forward step-bystep regression model were Vx during upsweep, Vy and Vx during insweep (r2 = 0.69). For overall velocity, the variables that most fit the regression model were Vx during upsweep, Vy during second downbeat and Vz during entry (r2= 0.94). In order to reduce dV, butterfliers should increase hand’s velocity in all orthogonal components at the end of the underwater path, should increase the vertical velocity durin

Swimming bioenergetics: integrating biomechanical and physiological data into a coherent biophysical model for performance and training

The purpose of the present paper is to synthesise a number of scientific contributions of our research group, into a coherent corpus of knowledge related to swimming biophysics, specially centred on the availability and use of energy in swimming. After an introductory part that intends to underline the relevance of this approach base on the conceptualization of the swimmer, and swimming action itself, as a thermodynamic system and its mechanical output, we will survey a number of studies and respective contributions for a more advanced understanding of swimming performance, that can be transferred into training and enhancement of swimmers’ working capacity. Most of the studies referred were conducted over samples of swimmers of both genders and of different types, from university/participative swimmers to Portuguese elite swimmers, crossing the large population of trained national level swimmers. Those swimmers were studied in the four different competitive swimming strokes, accomplishing progressive protocols based over distances of 200 m. Physiologic parameters like VO2 (and associated ventilatory and respiratory parameters), post exercise capillary blood [La-] peaks, and heart rate, were directly measured. Kinematical parameters were also measured in the different studies, ranging from simple semi-quantitative parameters, like stroke length (SL), and stroke frequency (SF), to more elaborated biomechanical data, like intracyclic speed fluctuations and propulsive segments kinematics. The focus of interest ranged from swimming economy of different strokes and genders (and of different technical alternatives of the same stroke), to the effects over energy cost of intracyclic speed fluctuations. Energetic input determinant factors, like swimming VO2 kinetics, including VO2 slow component, and VO2 time limit, and its determinants, will also be analysed

The influence of stroke mechanics into energy cost of elite swimmers

The purpose of this study was to analyze the relationships between energy cost (C), swimming velocity (v), stroke frequency (SF) and stroke length (SL) in toplevel swimmers. Eighteen elite swimmers (four freestylers, five backstrokers, five breaststrokers and four butterflyers) performed an intermittent set of n 9 200 m swims (n B 8) with increasing velocity. The oxygen consumption was measured breath-by-breath by a portable metabolic cart (K4 b2, Cosmed, Rome, Italy). A respiratory snorkel and valve system with low hydrodynamic resistance was used to measure pulmonary ventilation and collect expiratory gases. Blood samples were taken from the ear lobe before and after each swim to analyze the blood lactate concentration (YSI 1500L, Yellow Springs, OH, USA). At Backstroke, Breaststroke and Butterfly strokes, increases of SF were associated to increases of C, even when controlling the v. The increases in SL only promoted significant decreases in the C in Breaststroke. There was a significant and polynomial relationship between v and SF for all competitive swimming techniques. The polynomial relationship between v and SL was significant only in Freestyle and Butterfly stroke. Partial correlations between v and SF controlling the effect of SL and between v and SL controlling the effect of SF, were positive and significant for all techniques. It is concluded that manipulation of stroke mechanics variables (SF and SL) may be one of the factors through which C in competitive swimming can be altered for a given v

Attacks by “Anonymous” WikiLeaks Proponents not Anonymous

On November 28, 2010, the world started watching the whistle blower website WikiLeaks to begin publishing part of the 250,000 US Embassy Diplomatic cables. These confidential cables provide an insight on U.S. international affairs from 274 different embassies, covering topics such as analysis of host countries and leaders and even requests for spying out United Nations leaders.\ud The release of these cables has caused reactions not only in the real world, but also on the Internet. In fact, a cyberwar started just before the initial release. Wikileaks has reported that their servers were experiencing distributed denial-of-service attacks (DDoS). A DDoS attack consists of many computers trying to overload a server by firing a high number of requests, leading ultimately to service disruption. In this case, the goal was to avoid the release of the embassy cables.\ud After the initial cable release, several companies started severed ties with WikiLeaks. One of the first was Amazon.com, that removed the WikiLeaks web- site from their servers. Next, EveryDNS, a company in which the domain wikileaks.org was registered, dropped the domain entries from its servers. On December 4th, PayPal cancelled the account that WikiLeaks was using to receive on-line donations. On the 6th, Swiss bank PostFinance froze the WikiLeaks assets and Mastercard stopped receiving payments to the WikiLeaks account. Visa followed Mastercard on December 7th.\ud These reactions caused a group of Internet activists (or “hacktivists”) named Anonymous to start a retaliation against PostFinance, PayPay, MasterCard, Visa, Moneybrookers.com and Amazon.com, named “Operation Payback”. The retaliation was performed as DDoS attacks to the websites of those companies, disrupting their activities (except for the case of Amazon.com) for different periods of time.\ud The Anonymous group consists of volunteers that use a stress testing tool to perform the attacks. This tool, named LOIC (Low Orbit Ion Cannon), can be found both as a desktop application and as a Web page.\ud Even though the group behind the attacks claims to be anonymous, the tools they provide do not offer any security services, such as anonymization. As a consequence, a hacktivist that volunteers to take part in such attacks, can be traced back easily. This is the case for both current versions of the LOIC tool. Therefore, the goal of this report is to present an analysis of privacy issues in the context of these attacks, and raise awareness on the risks of taking part in them

Estudo piloto da resposta bioenergética a diferentes ritmos respiratórios na técnica de mariposa

Introdução e objectivos: O objectivo do presente trabalho foi o de efectuar um estudo piloto, comparando a resposta bioenergética à adopção de diferentes ritmos respiratórios na técnica de Mariposa. Material e métodos: Foram estudadas duas nadadoras e um nadador de nível nacional (17.0±3.6 anos de idade, 159.0±12.0cm de estatura, 56.9±10.3Kg de massa corporal e 18.0±8.9% de massa gorda). Cada nadador efectuou, numa piscina de 25m, 3 repetições de 200m, a uma velocidade tão próxima quanto possível da máxima. De forma aleatória, em cada repetição, os nadadores realizaram inspirações frontais em todos os ciclo gestuais (1:1F), uma inspiração frontal em cada dois ciclos gestuais (1:2F) e ciclo gestuais inspirando pelo tubo de condução de gases, mas sem a emersão da face (0:0). Avaliaram-se as trocas gasosas e os parâmetros cardiorespiratórios através de um oxímetro breath-by-breath (K4 b2, Cosmed, Itália). Uma válvula de baixa resistência hidrodinâmica encontrava-se ligada ao oxímetro, permitindo a recolha das amostras de gases a analisar (Toussaint et al., 1987; Keskinen et al. 2003). Foram retiradas amostras de sangue capilar da orelha antes, imediatamente após cada 200m e 1, 3, 5 e 7 minutos depois do fim do protocolo, para a avaliação da concentração sérica de lactato (YSI ASPECTOS BIOLÓGICOS DO DESPORTO E DO EXERCÍCIO Revista Portuguesa de Ciências do Desporto, 2004, vol. 4, nº 2 (suplemento) [237–274] 241 1500L, Yellow Springs, EUA). Foi utilizado um cardiofrequencímetro para medição da frequência cardíaca (Vantage NV, POLAR, Finlândia). Foi avaliado o consumo máximo de oxigénio relativo (VO2-max), o consumo líquido de oxigénio (VO2- net=VO2-max-VO2-repouso), a concentração máxima de lactato (La-max), a concentração líquida de lactato (La-net= Lamax- La-repouso), o quociente respiratórios (R), o volume ventilatório (VV) e a frequência cardíaca (FC). Também foram avaliados o dispêndio energético total (Etot) calculado com base no VO2-net e na La-net, transformada em equivalentes de VO2 através da constante de 2.7 ml.kg.-1.mmol-1 (di Prampero et al., 1978) e o custo energético (CE= Etot .velocidade-1). Principais resultados e conclusões: O VO2-max foi 26.0% superior utilizando o ritmo de 1:1F do que o ritmo de 0:0 e 7.25% superior do que o ritmo de 1:2F. O VO2-net foi respectivamente 27.3% e 9.94% superior adoptando o ritmo 1:1F do que os ritmos de 0:0 e de 1:2F. O ritmo que exigiu um menor Etot foi o de 0:0, com menos 19.24% do que o 1:1F e menos 9.44% do que o 1:2F. O CE foi substancialmente superior usando o ritmo de 1:1F do que o ritmo de 0:0, com uma variação média de 23.8%. O VV foi superior usando o 1:1F do que o 1:2F ou o 0:0 em respectivamente, 14.57% e 3.19%. Em conclusão, a adopção de diferentes ritmos respiratórios induzirá alterações na resposta bioenergética ao nadar a técnica de Mariposa. Contudo, sugere-se um estudo com uma amostra mais alargada, procurando aferir se as tendências manifestadas no presente estudo revelam robustez do ponto de vista estatístico. Mesmo assim, parece que a diminuição do número de actos inspiratórios promove uma redução dramática do Etot e do CE. Logo, em contextos competitivos, os mariposistas terão algumas vantagens em reduzir, tanto quant

Aportaciones desde la biomecánica de la natación de competición

A natação é uma modalidade individual, cíclica e fechada, pelo que, no respectivo quadro de factores determinantes do sucesso competitivo, a optimização do gesto técnico desempenha um papel determinante.info:eu-repo/semantics/publishedVersio

Estudo da relação entre o custo energético e a mecânica gestual mariposa

Introdução e objectivos: Foi objectivo do presente estudo identificar a relação entre variáveis bioenergéticas (gasto energético e custo energético) e biomecânicas (parâmetros do ciclo gestual) ao longo de um leque de velocidades na técnica de Mariposa. Material e métodos: Três nadadores e uma nadadora de nível internacional foram submetidos a um protocolo incremental de 200m a Mariposa. A velocidade inicial foi de 1.18 m.s-1 para os nadadores e de 1.03 m.s-1 para a nadadora. A cada 200m a velocidade apresentava um incremento de 0.05.s-1 até o nadador atingir a exaustão. Avaliaram-se as trocas gasosas e os parâmetros cardiorespiratórios através de um oxímetro breathby- breath (K4 b2, Cosmed, Itália). Uma válvula de baixa resistência hidrodinâmica encontrava-se ligada ao oxímetro, permitindo a recolha das amostras de gases a analisar (Toussaint et al., 1987; Keskinen et al. 2003). Foram colhidas amostras de sangue capilar da orelha antes, imediatamente após cada 200m e 1, 3, 5 e 7 minutos depois do fim do protocolo, para a avaliação da concentração sérica de lactato (YSI 1500L, Yellow Springs, EUA). Foi calculado o dispêndio energético total (Etot), o custo energético (CE), a frequência gestual (FG), a distância de ciclo (DC), a velocidade média de deslocamento (V) e o índice de braçada (IB) para cada percurso, e calculado o valor médio para cada patamar de 200m. Foram calculadas rectas de regressão individuais, assim como os respectivos coeficientes de determinação e de correlação entre as variáveis bioenergéticas e as variáveis biomecânicas em estudo (p£ 0.05). Principais resultados e conclusões: Os coeficientes de correlação entre o Etot e a V, entre o CE e a FG e entre o CE e o IB apresentaram significado estatístico em todos os nadadores. Da relação entre o CE e a DC, apenas uma equação de regressão apresentou o coeficiente de correlação com significado estatístico. A relação entre a FG e a V, bem como, a relação entre o IB e a V foram significativas em todos os nadadores. Apenas duas equações de regressão apresentaram coeficientes de correlação significativos entre a V e a DC. Em conclusão, a amostra apresentou uma elevada variação inter-individual na relação entre as variáveis bioenergéticas e as variáveis biomecânicas em estudo, a Mariposa. Assim, sugere-se a análise individual da relação entre a V, a FG e a DC, com o intuito de identificar o ponto de deflexão da DC em função da V. Desta forma, será possível determinar as intensidades de treino adequadas com o objectivo de melhorar o custo energético específico de transporte